POI使用公式的問題，POI對excel函數的支持

一、問題

最近在使用POI操作excel文件時，會報如下錯誤：

org.apache.poi.ss.formula.eval.NotImplementedException: Error evaluating cell 'AAA'!E5
	at org.apache.poi.ss.formula.WorkbookEvaluator.addExceptionInfo(WorkbookEvaluator.java:332)
	at org.apache.poi.ss.formula.WorkbookEvaluator.evaluateAny(WorkbookEvaluator.java:273)
	at org.apache.poi.ss.formula.WorkbookEvaluator.evaluate(WorkbookEvaluator.java:205)
	at org.apache.poi.hssf.usermodel.HSSFFormulaEvaluator.evaluateFormulaCellValue(HSSFFormulaEvaluator.java:374)
	at org.apache.poi.hssf.usermodel.HSSFFormulaEvaluator.evaluateFormulaCell(HSSFFormulaEvaluator.java:234)
	at com.xmas.kenbb.test.PoiTest.main(PoiTest.java:40)
Caused by: org.apache.poi.ss.formula.eval.NotImplementedException: Error evaluating cell 'WinProbEst - Table 1-1'!J5
	at org.apache.poi.ss.formula.WorkbookEvaluator.addExceptionInfo(WorkbookEvaluator.java:332)
	at org.apache.poi.ss.formula.WorkbookEvaluator.evaluateAny(WorkbookEvaluator.java:273)
	at org.apache.poi.ss.formula.WorkbookEvaluator.evaluateReference(WorkbookEvaluator.java:702)
	at org.apache.poi.ss.formula.SheetRefEvaluator.getEvalForCell(SheetRefEvaluator.java:48)
	at org.apache.poi.ss.formula.SheetRangeEvaluator.getEvalForCell(SheetRangeEvaluator.java:74)
	at org.apache.poi.ss.formula.LazyRefEval.getInnerValueEval(LazyRefEval.java:43)
	at org.apache.poi.ss.formula.eval.OperandResolver.chooseSingleElementFromRef(OperandResolver.java:179)
	at org.apache.poi.ss.formula.eval.OperandResolver.getSingleValue(OperandResolver.java:62)
	at org.apache.poi.ss.formula.WorkbookEvaluator.dereferenceResult(WorkbookEvaluator.java:570)
	at org.apache.poi.ss.formula.WorkbookEvaluator.evaluateFormula(WorkbookEvaluator.java:521)
	at org.apache.poi.ss.formula.WorkbookEvaluator.evaluateAny(WorkbookEvaluator.java:263)
	... 4 more
Caused by: org.apache.poi.ss.formula.eval.NotImplementedException: Error evaluating cell 'BBB'!I5
	at org.apache.poi.ss.formula.WorkbookEvaluator.addExceptionInfo(WorkbookEvaluator.java:332)
	at org.apache.poi.ss.formula.WorkbookEvaluator.evaluateAny(WorkbookEvaluator.java:273)
	at org.apache.poi.ss.formula.WorkbookEvaluator.evaluateReference(WorkbookEvaluator.java:702)
	at org.apache.poi.ss.formula.SheetRefEvaluator.getEvalForCell(SheetRefEvaluator.java:48)
	at org.apache.poi.ss.formula.SheetRangeEvaluator.getEvalForCell(SheetRangeEvaluator.java:74)
	at org.apache.poi.ss.formula.LazyRefEval.getInnerValueEval(LazyRefEval.java:43)
	at org.apache.poi.ss.formula.eval.OperandResolver.chooseSingleElementFromRef(OperandResolver.java:179)
	at org.apache.poi.ss.formula.eval.OperandResolver.getSingleValue(OperandResolver.java:62)
	at org.apache.poi.ss.formula.eval.TwoOperandNumericOperation.singleOperandEvaluate(TwoOperandNumericOperation.java:29)
	at org.apache.poi.ss.formula.eval.TwoOperandNumericOperation.evaluate(TwoOperandNumericOperation.java:36)
	at org.apache.poi.ss.formula.functions.Fixed2ArgFunction.evaluate(Fixed2ArgFunction.java:33)
	at org.apache.poi.ss.formula.OperationEvaluatorFactory.evaluate(OperationEvaluatorFactory.java:119)
	at org.apache.poi.ss.formula.WorkbookEvaluator.evaluateFormula(WorkbookEvaluator.java:503)
	at org.apache.poi.ss.formula.WorkbookEvaluator.evaluateAny(WorkbookEvaluator.java:263)
	... 13 more
Caused by: org.apache.poi.ss.formula.eval.NotImplementedException: Error evaluating cell 'BBB'!E5
	at org.apache.poi.ss.formula.WorkbookEvaluator.addExceptionInfo(WorkbookEvaluator.java:332)
	at org.apache.poi.ss.formula.WorkbookEvaluator.evaluateAny(WorkbookEvaluator.java:273)
	at org.apache.poi.ss.formula.WorkbookEvaluator.evaluateReference(WorkbookEvaluator.java:702)
	at org.apache.poi.ss.formula.SheetRefEvaluator.getEvalForCell(SheetRefEvaluator.java:48)
	at org.apache.poi.ss.formula.SheetRangeEvaluator.getEvalForCell(SheetRangeEvaluator.java:74)
	at org.apache.poi.ss.formula.LazyRefEval.getInnerValueEval(LazyRefEval.java:43)
	at org.apache.poi.ss.formula.eval.OperandResolver.chooseSingleElementFromRef(OperandResolver.java:179)
	at org.apache.poi.ss.formula.eval.OperandResolver.getSingleValue(OperandResolver.java:62)
	at org.apache.poi.ss.formula.eval.TwoOperandNumericOperation.singleOperandEvaluate(TwoOperandNumericOperation.java:29)
	at org.apache.poi.ss.formula.eval.TwoOperandNumericOperation.evaluate(TwoOperandNumericOperation.java:35)
	at org.apache.poi.ss.formula.functions.Fixed2ArgFunction.evaluate(Fixed2ArgFunction.java:33)
	at org.apache.poi.ss.formula.OperationEvaluatorFactory.evaluate(OperationEvaluatorFactory.java:119)
	at org.apache.poi.ss.formula.WorkbookEvaluator.evaluateFormula(WorkbookEvaluator.java:503)
	at org.apache.poi.ss.formula.WorkbookEvaluator.evaluateAny(WorkbookEvaluator.java:263)
	... 25 more
Caused by: org.apache.poi.ss.formula.eval.NotImplementedException: Error evaluating cell 'BBB'!F52
	at org.apache.poi.ss.formula.WorkbookEvaluator.addExceptionInfo(WorkbookEvaluator.java:332)
	at org.apache.poi.ss.formula.WorkbookEvaluator.evaluateAny(WorkbookEvaluator.java:273)
	at org.apache.poi.ss.formula.WorkbookEvaluator.evaluateReference(WorkbookEvaluator.java:702)
	at org.apache.poi.ss.formula.SheetRefEvaluator.getEvalForCell(SheetRefEvaluator.java:48)
	at org.apache.poi.ss.formula.SheetRangeEvaluator.getEvalForCell(SheetRangeEvaluator.java:74)
	at org.apache.poi.ss.formula.LazyAreaEval.getRelativeValue(LazyAreaEval.java:51)
	at org.apache.poi.ss.formula.LazyAreaEval.getRelativeValue(LazyAreaEval.java:45)
	at org.apache.poi.ss.formula.eval.AreaEvalBase.getValue(AreaEvalBase.java:128)
	at org.apache.poi.ss.formula.functions.Sumproduct.evaluateAreaSumProduct(Sumproduct.java:157)
	at org.apache.poi.ss.formula.functions.Sumproduct.evaluate(Sumproduct.java:77)
	at org.apache.poi.ss.formula.OperationEvaluatorFactory.evaluate(OperationEvaluatorFactory.java:132)
	at org.apache.poi.ss.formula.WorkbookEvaluator.evaluateFormula(WorkbookEvaluator.java:503)
	at org.apache.poi.ss.formula.WorkbookEvaluator.evaluateAny(WorkbookEvaluator.java:263)
	... 37 more
Caused by: org.apache.poi.ss.formula.eval.NotImplementedFunctionException: NORMDIST
	at org.apache.poi.ss.formula.functions.NotImplementedFunction.evaluate(NotImplementedFunction.java:40)
	at org.apache.poi.ss.formula.OperationEvaluatorFactory.evaluate(OperationEvaluatorFactory.java:132)
	at org.apache.poi.ss.formula.WorkbookEvaluator.evaluateFormula(WorkbookEvaluator.java:503)
	at org.apache.poi.ss.formula.WorkbookEvaluator.evaluateAny(WorkbookEvaluator.java:263)
	... 48 more

原來，源錯誤在於最近一個異常：

NotImplementedFunctionException: NORMDIST

二、查找資料

剛開始時看不太明白這個異常的意思，大概是英文領悟能力欠佳吧。

於是，查看官方文檔：http://poi.apache.org/spreadsheet/formula.html，看到“公式支持”裏有說明，說什麼支持什麼還不支持，畢竟excel的東西不少，要完全支持得需多方面的支持。看到“Supported Functions”裏有這麼一段話：

The methods you need are available on org.apache.poi.ss.formula.eval.FunctionEval. To find which functions your copy of Apache POI supports, use getSupportedFunctionNames() to get a list of the implemented function names. For the list of functions that POI knows the name of, but doesn't currently implement, use getNotSupportedFunctionNames()

意思是說，目前POI支持了部分函數，尚有部分函數未提供支持，試着把它們打印出來，如下：

支持的函數：

[ABS, ACOS, ACOSH, ADDRESS, AND, ASIN, ASINH, ATAN, ATAN2, ATANH, AVEDEV, AVERAGE, CEILING, CHAR, CHOOSE, CLEAN, CODE, COLUMN, COLUMNS, COMBIN, CONCATENATE, COS, COSH, COUNT, COUNTA, COUNTBLANK, COUNTIF, DATE, DAY, DAYS360, DEGREES, DEVSQ, DOLLAR, ERROR.TYPE, EVEN, EXACT, EXP, FACT, FALSE, FIND, FIXED, FLOOR, FV, HLOOKUP, HOUR, HYPERLINK, IF, INDEX, INDIRECT, INT, INTERCEPT, IPMT, IRR, ISBLANK, ISERROR, ISLOGICAL, ISNA, ISNONTEXT, ISNUMBER, ISREF, ISTEXT, LARGE, LEFT, LEN, LN, LOG, LOG10, LOOKUP, LOWER, MATCH, MAX, MAXA, MEDIAN, MID, MIN, MINA, MINUTE, MIRR, MOD, MODE, MONTH, NA, NOT, NOW, NPER, NPV, ODD, OFFSET, OR, PERCENTILE, PI, PMT, POISSON, POWER, PPMT, PRODUCT, PROPER, PV, RADIANS, RAND, RANK, RATE, REPLACE, REPT, RIGHT, ROMAN, ROUND, ROUNDDOWN, ROUNDUP, ROW, ROWS, SEARCH, SECOND, SIGN, SIN, SINH, SLOPE, SMALL, SQRT, STDEV, SUBSTITUTE, SUBTOTAL, SUM, SUMIF, SUMPRODUCT, SUMSQ, SUMX2MY2, SUMX2PY2, SUMXMY2, T, TAN, TANH, TEXT, TIME, TODAY, TRIM, TRUE, TRUNC, UPPER, VALUE, VAR, VARP, VLOOKUP, WEEKDAY, YEAR]

不支持的函數：
[AREAS, ASC, AVERAGEA, BETADIST, BETAINV, BINOMDIST, CELL, CHIDIST, CHIINV, CHITEST, CONFIDENCE, CORREL, COVAR, CRITBINOM, DATEDIF, DATESTRING, DATEVALUE, DAVERAGE, DB, DBCS, DCOUNT, DCOUNTA, DDB, DGET, DMAX, DMIN, DPRODUCT, DSTDEV, DSTDEVP, DSUM, DVAR, DVARP, EXPONDIST, FDIST, FINDB, FINV, FISHER, FISHERINV, FORECAST, FREQUENCY, FTEST, GAMMADIST, GAMMAINV, GAMMALN, GEOMEAN, GETPIVOTDATA, GROWTH, HARMEAN, HYPGEOMDIST, INFO, ISERR, ISPMT, KURT, LEFTB, LENB, LINEST, LOGEST, LOGINV, LOGNORMDIST, MDETERM, MIDB, MINVERSE, MMULT, N, NEGBINOMDIST, NORMDIST, NORMINV, NORMSDIST, NORMSINV, NUMBERSTRING, PEARSON, PERCENTRANK, PERMUT, PHONETIC, PROB, QUARTILE, REPLACEB, RIGHTB, RSQ, SEARCHB, SKEW, SLN, STANDARDIZE, STDEVA, STDEVP, STDEVPA, STEYX, SYD, TDIST, TIMEVALUE, TINV, TRANSPOSE, TREND, TRIMMEAN, TTEST, TYPE, USDOLLAR, VARA, VARPA, VDB, WEIBULL, ZTEST]

三、總結

如果操作的excel需要使用到不被支持的函數，就需要自行添加相關函數的支持，或者考慮使用其它技術插件了。

POI註冊一個函數大概是使用這個方法：FunctionEval.registerFunction(name, func);